/* kf_tan.c -- float version of k_tan.c
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include "fdlibm.h"
static const float one = 1.0000000000e+00, /* 0x3f800000 */
    pio4 = 7.8539812565e-01, /* 0x3f490fda */
    pio4lo = 3.7748947079e-08, /* 0x33222168 */
    T[] = {
        3.3333334327e-01, /* 0x3eaaaaab */
        1.3333334029e-01, /* 0x3e088889 */
        5.3968254477e-02, /* 0x3d5d0dd1 */
        2.1869488060e-02, /* 0x3cb327a4 */
        8.8632395491e-03, /* 0x3c11371f */
        3.5920790397e-03, /* 0x3b6b6916 */
        1.4562094584e-03, /* 0x3abede48 */
        5.8804126456e-04, /* 0x3a1a26c8 */
        2.4646313977e-04, /* 0x398137b9 */
        7.8179444245e-05, /* 0x38a3f445 */
        7.1407252108e-05, /* 0x3895c07a */
        -1.8558637748e-05, /* 0xb79bae5f */
        2.5907305826e-05, /* 0x37d95384 */
    };

float
__kernel_tanf(float x, float y, int iy)
{
    float z, r, v, w, s;
    __int32_t ix, hx;
    GET_FLOAT_WORD(hx, x);
    ix = hx & 0x7fffffff; /* high word of |x| */
    if (ix < 0x31800000) /* x < 2**-28 */
    {
        if ((int)x == 0) { /* generate inexact */
            if ((ix | (iy + 1)) == 0)
                return one / fabsf(x);
            else
                return (iy == 1) ? x : -one / x;
        }
    }
    if (ix >= 0x3f2ca140) { /* |x|>=0.6744 */
        if (hx < 0) {
            x = -x;
            y = -y;
        }
        z = pio4 - x;
        w = pio4lo - y;
        x = z + w;
        y = 0.0;
    }
    z = x * x;
    w = z * z;
    /* Break x^5*(T[1]+x^2*T[2]+...) into
     *	  x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
     *	  x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
     */
    r = T[1] + w * (T[3] + w * (T[5] + w * (T[7] + w * (T[9] + w * T[11]))));
    v = z *
        (T[2] + w * (T[4] + w * (T[6] + w * (T[8] + w * (T[10] + w * T[12])))));
    s = z * x;
    r = y + z * (s * (r + v) + y);
    r += T[0] * s;
    w = x + r;
    if (ix >= 0x3f2ca140) {
        v = (float)iy;
        return (float)(1 - ((hx >> 30) & 2)) *
               (v - (float)2.0 * (x - (w * w / (w + v) - r)));
    }
    if (iy == 1)
        return w;
    else { /* if allow error up to 2 ulp,
			   simply return -1.0/(x+r) here */
        /*  compute -1.0/(x+r) accurately */
        float a, t;
        __int32_t i;
        z = w;
        GET_FLOAT_WORD(i, z);
        SET_FLOAT_WORD(z, i & 0xfffff000);
        v = r - (z - x); /* z+v = r+x */
        t = a = -(float)1.0 / w; /* a = -1.0/w */
        GET_FLOAT_WORD(i, t);
        SET_FLOAT_WORD(t, i & 0xfffff000);
        s = (float)1.0 + t * z;
        return t + a * (s + t * v);
    }
}
